When one of the knitting feeds in multi-feed circular knitting machines is using a yarn supply quantity of yarn tension that differs from that of the other feeds, an unattractive defect is the result, especially in plain or unpatterned goods, which precludes use of the goods. It is therefore known to monitor the yarn tension or yarn supply quantity, for example with manual gauges, at the individual knitting stations, and if deviations that would lead to defective goods are found, to make a thorough check. However, such a check may come relatively late after the defect has occurred, by which time a large quantity of defective goods would already then have been produced.
From German Pat. No. 36 27 731, a yarn supply means having electronic yarn tension regulation is known, which has a rotatably supported yarn wheel that supplies the yarn in a substantially slip-free manner. The drive of the yarn wheel, with which other yarn guide elements are also associated, is done with the aid of a stepping motor, which is controlled with an electronic control. The electronic control is substantially a voltage controlled oscillator (VCO), which generates the stepping pulses for the stepping motor. The VCO receives its input signal from yarn tension sensing means that are disposed after the yarn wheel in the course of yarn travel. With the aid of the yarn tension sensing means, a signal that is characteristic for the yarn tension is generated, with the aid of which the VCO is subsequently regulated in such a manner that the yarn tension remains substantially constant.
The known yarn supply means thus receives two electrical signals, one of which characterizes the yarn tension and the other of which, as a frequency signal at the output of the oscillator, characterizes the yarn supply quantity or in other words the yarn quantity per unit of time.